So far, there's been no 4S equivalent to the iPhone 4's "Antennagate." But as folks put their new gadget through its paces, some early complaints have appeared on online message boards.

Some of these may be early-run blips (that's how we're going to categorize the problems that some customers had activating their phones over the weekend). Whether they become enduring causes of headaches remains to be seen. (Apple did not immediately respond to our request for comment.)

"Sprint, we need some answer. Are you guys doing iPhone specific throttling?" one person posted. "You will lose your customer if the customer finding their iPhone unusable ... "

This isn't the first time Sprint's speed has come into question. In PCMag's June survey of the fastest mobile networks, Sprint trailed Verizon and AT&T in most regions of the country.

A Sprint news release said Friday was the biggest sales day of a mobile device in its history, surpassing expectations.

"As always, Sprint is carefully monitoring the performance of the 3G network," Sprint spokesman Scott Sloat said in a written statement to CNN. "We are looking into a small number of reports of slow data speeds when using the iPhone 4S, however there are also reports showing that Sprint's network is the fastest, such as the Gizmodo report that came out earlier today."

2. Weak battery

At the October 4 presentation unveiling the iPhone 4S, Phil Schiller , Apple vice president for product management, praised its "fantastic battery life" that would allow people to talk for eight hours before needing to charge the device again.

"After three days of non-stop testing, we had a clear answer: The iPhone 4S is generally more power hungry than the iPhone 4, and Apple has only made the slightest capacity improvement to the iPhone 4S's battery," the review reads. "Moreover, whereas Apple underpromised with the iPhone 4's battery estimates, it comes closer to overpromising with the iPhone 4S."

The review says that using Wi-Fi consistently and using the phone mainly for calls and Web browsing wears the battery out at roughly the same speed as the iPhone 4, while playing videos and music or using a 3G connection will drain it faster.

3. Siri outside the United States

Demand for the iPhone 4S was clearly global. But one of its biggest selling-points, the built-in voice assistant Siri, only works fully stateside.

While many of its built-in features work anywhere, location based actions don't. So, using Siri to, say, find a local business or get driving directions, doesn't work elsewhere.

Even queries asking for the time of day weren't working in Canada, according to some reports.

Compounding that problem (for some folks both inside and outside the U.S.) is the fact that Siri has trouble understanding heavy accents.

It currently works with English, French and German (with more languages coming). But non-native English speakers have reported lots of trouble.

We can only imagine how Siri's doing in Scotland.

4. Camera problems

Another big selling point for the 4S is its 8-megapixel camera, which is a pretty significant jump from the 5 megapixels on the iPhone 4 and 3 megapixels on the iPhone 3GS.

Reviews of the images the phone renders have been overwhelmingly positive, with users reporting a major difference in clarity.

But the same "shutter speed" issues users have complained about on previous iPhones appear to be back again.

In a forum discussion on Apple's site, some reported that when they'd take a photo, the camera got stuck with the shutter closed or moved really slowly. Others said the camera wasn't working at all, although it looks like they were largely able to fix that by turning the phone off and restarting.

5. Screen appearance

At least it looks like there's an easy answer for this one.

Some buyers are reporting a yellowish tint or spots on the screen of their phones, making the resolution fuzzier than older phones.

This is an issue that previous iPhones had as well. While Apple has never officially explained it (presumably because it hasn't impacted enough people), technicians have reportedly said it's residue from the manufacturing process.